A polycondensation preparation process for high-strength bio-based polyamide denim yarn fibers

Abstract

This invention relates to the field of bio-based polyamide synthesis technology and discloses a polycondensation preparation process for high-strength bio-based polyamide denim yarn fibers. The process includes: adding bio-based diacid, diamine, and lignin-derived triamine into a reactor and pre-condensing at 210°C to 230°C to generate oligomers; in the deep polycondensation stage, self-flash disturbance is induced by periodically adjusting the vacuum level to drive the uniform migration of branched modified components; when the stirring torque reaches the preset maximum process torque value, vanillic acid monoester is added for end capping. This invention utilizes pulsed pressure fluctuations to break the mass transfer resistance of the high-viscosity system, ensuring uniform distribution of branched nodes throughout the entire domain. The constructed isotropic topological network is based on the shear-thinning characteristics of the product and forms a three-dimensional stress diffusion system in the fibrous state, improving load transfer efficiency and avoiding the risk of fibrillation in denim fabrics under heavy washing conditions.

Description

Technical Field

[0001] This invention relates to a polycondensation preparation process for high-strength bio-based polyamide denim yarn fibers, belonging to the field of bio-based polyamide synthesis technology. Background Technology

[0002] Currently, the preparation of high-strength fibers in the field of polyamide synthesis usually focuses on increasing molecular weight. Existing processes increase polymer viscosity by extending the polycondensation time and increasing the vacuum level, and then combine this with high-ratio stretching in subsequent spinning to obtain the fiber's mechanical properties. In practical applications, bio-based polyamide denim fibers need to withstand the corrosive effects of the high acid and alkali environment of indigo dyeing and the friction of heavy stone washing processes. The linear polymer chains obtained by physical stretching have single-chain slip defects when subjected to force, and there is a lack of physical or chemical cross-linking points between molecular chains, resulting in fibrillation. The increased depth of the polycondensation reaction causes the melt viscosity to increase exponentially, leading to excessive melt conveying pressure and the risk of local thermal degradation in industrial continuous polymerization spinning equipment.

[0003] Although mass transfer can be enhanced by improving reactor impeller configuration or increasing condensation efficiency, hardware improvements cannot precisely intervene in the topological network at the molecular scale. Bottlenecks in the polymerization process control logic are key constraints on fiber performance. For example, Chinese invention patent CN108586265A discloses pentanediamine sebacate and its crystals, which ensures the purity and stability of the polymerization raw materials through monomer salt purification and crystallization. However, in the deep polycondensation stage of fiber preparation, the traditional constant high vacuum mode is still used. Under high-viscosity melt conditions, static purity optimization cannot break through the mass transfer barrier. When branched modified components are introduced, the lack of dynamic micro-control of pressure easily leads to local enrichment of components and induces microgel points, making it difficult to construct a spatially uniform distribution within the fiber that resists heavy water washing and peeling. To address the aforementioned challenges, existing technologies attempt to introduce multifunctional monomers to construct branched structures. However, under ultra-high viscosity melt conditions, the diffusion coefficient of branched modified components drops sharply, leading to localized microgel points caused by mass transfer resistance and disruption of fiber-forming properties. The main shortcomings are: 1. Branched components accumulate locally within the melt due to impaired diffusion, inducing uncontrolled cross-linking and deteriorating fiber-forming performance; 2. Non-uniform topological nodes evolve into stress concentration centers when the fiber is under stress, resulting in a decrease in strength after multiple washes of bio-based products; 3. Traditional constant high vacuum processes cannot break the mass transfer barrier, making it difficult to construct a uniform topological anchoring network at the molecular level. The contradiction between viscosity and mass transfer restricts the application potential of bio-based polyamides in the field of high-performance denim apparel.

[0004] Therefore, how to force the modified components to cross the diffusion barrier under the high viscosity barrier in the later stage of polycondensation and construct a spatially uniform topological anchoring network has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber, comprising the following steps:

[0006] Step 101: The raw material system is fed into the polycondensation reactor. The raw material system includes bio-based dicarboxylic acid monomer, bio-based diamine monomer, and branched modification component. The branched modification component is a lignin-derived triamine with a three-symmetric structure, and the mass percentage of the branched modification component in the raw material system is 0.15% to 0.45%. Among them, the bio-based dicarboxylic acid monomer is bio-based sebacic acid with an acid value of 548 mg / g to 552 mg / g and an ash content of no more than 0.01 wt%, and the bio-based diamine monomer is bio-based pentanediamine with a purity of no less than 99.5% and a moisture content of no more than 500 ppm.

[0007] Step 102: Under normal temperature and pressure conditions of 210°C to 230°C, the bio-based dicarboxylic acid monomer and the bio-based diamine monomer are reacted to generate oligomers.

[0008] Step 103: Under conditions of 265℃ to 280℃, periodically adjust the vacuum level in the polycondensation reactor to induce deep polycondensation of the oligomers. A single adjustment cycle includes: opening the vacuum compensation valve, adjusting the vacuum level from below 50 Pa to 500 Pa to 800 Pa within 15 to 20 seconds to induce self-flash turbulence inside the melt, and restoring the vacuum level to below 50 Pa within 10 seconds; repeating the adjustment cycle every 15 minutes until the stirring torque of the polycondensation reactor reaches 92% of the preset maximum process torque value.

[0009] Step 104: Add 0.15% to 0.55% by mass of bio-based vanillic acid monoester into the polycondensation reactor and continue the reaction until the stirring torque is constant.

[0010] Preferably, the primary amine content of the branched modified component is 12.5 wt% to 13.8 wt%, and its molecular weight distribution index is not greater than 1.2; in step 103, the stirring speed of the polycondensation reactor is controlled so that the shear rate of the melt during the bonding stage of the branched modified component and the oligomer is kept constant, wherein the fluctuation deviation of the stirring speed is controlled within ±2% of the preset reference speed to suppress uncontrolled gelation of the melt locally.

[0011] Preferably, in step 103, the self-flash evaporation disturbance generated by the vacuum degree correction process drives the branched modified component to migrate to the middle segment of the polyamide molecular chain, so as to form spatially uniformly distributed branched nodes.

[0012] Preferably, the molar ratio of bio-based sebacic acid to bio-based pentanediamine is 1.0 to 1.01 to 1.03.

[0013] Preferably, in step 103, during the pressure holding stage after the vacuum level is restored to below 50 Pa, the branched modified component and the polyamide segment are covalently bonded.

[0014] Preferably, in step 103, when the mass percentage of the branched modified component in the raw material system is 0.25% to 0.35%, a branched polyamide with a star-shaped topology is obtained.

[0015] Preferably, in step 104, the amount of bio-based vanillic acid monoester added is such that the ratio of the terminal amino group content to the terminal carboxyl group content of the resulting bio-based polyamide is 0.95 to 1.05.

[0016] Preferably, in step 102, the water produced by the reaction is continuously removed by a condensation device until the number average molecular weight of the oligomer reaches 2,000 to 5,000.

[0017] Preferably, in step 103, the pressure difference generated during the vacuum degree recovery process... The following relationship must be satisfied: ,in, , This is the vacuum level value after the callback. This represents the vacuum level value before the callback.

[0018] Preferably, the apparent viscosity of the prepared bio-based polyamide in the molten state decreases non-linearly with increasing shear rate, and the viscosity decreases further as the shear rate increases from... Increase to Within the specified range, the apparent viscosity decreases by no less than 50%.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. In the polycondensation preparation of polyamide denim yarn, pulsed vacuum control induces a micro-flash evaporation effect, which solves the diffusion barrier of branched components in high-viscosity melts. During the deep polycondensation stage, the vacuum degree fluctuates periodically within the range, causing the residual trace small molecule by-products inside the melt to generate instantaneous self-pressurization. The resulting micro-disturbance overcomes the mass transfer resistance of high molecular weight polyamide melts, drives lignin-derived triamines to migrate uniformly to molecular chain segments and covalently bond, eliminates the local enrichment of branching points and the generation of microgel points, realizes the uniformity of the topological structure of polyamide molecular chains, and ensures the isotropic physical properties of the product.

[0021] 2. Constructing a quasar-shaped topological molecular chain structure enables bio-based polyamides to possess shear-thinning properties, breaking through the viscosity bottleneck of linear high molecular weight polyamides. The introduction of branched nodes alters the melt rheological behavior, causing the apparent viscosity of the product to decrease nonlinearly under the action of high shear fields at the discharge port and spinning components. This reduces the melt conveying pressure in continuous production processes, avoids the risk of local thermal degradation caused by drastically increasing the polycondensation temperature in pursuit of high strength, and improves production stability.

[0022] 3. Branched nodes construct a three-dimensional stress diffusion network between molecular chains, enhancing the structural stability of fibers under combined chemical and mechanical fields. Topological anchoring points are spatially uniformly distributed in the polyamide matrix. When fibers are subjected to the corrosive effects of indigo dyeing in high acid and alkali environments or the strong mechanical friction of denim stone washing, stress diffuses through the branched nodes to adjacent molecular chains in a network-like manner, inhibiting the sliding and breakage of single linear chains under stress, avoiding the fibrillation phenomenon that easily occurs in bio-based polyamides, and extending the washing life of high-strength denim fabrics. The torque threshold of the deep polycondensation stage is precisely controlled at the sealed end. With the addition of vanillic acid monoester, the molecular weight distribution and end-group properties of bio-based polyamides are regulated. The synergistic effect of vanillic acid monoester and pulsed vacuum cycle allows the polycondensation reaction to terminate rapidly when the preset mechanical strength point is reached, inhibiting the subsequent thermal degradation reaction, ensuring that the product has fiber-forming properties and color stability, and meeting the quality requirements of bio-based materials for high-performance denim apparel. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the overall principle of raw material coordination and reaction conditions in the bio-based polyamide polycondensation process of this invention.

[0024] Figure 2 This is a comparison diagram showing the effects of different branching modification component contents on melt rheological properties and fiber fibrillation in this invention.

[0025] Figure 3 This is a flowchart illustrating the polycondensation process of the present invention, which integrates pulsed vacuum regulation and torque end-capping control. Detailed Implementation

[0026] The present invention will be described in detail below with reference to specific embodiments. The following embodiments are intended to explain the present invention and not to limit the scope of protection of the present invention.

[0027] This invention provides a polycondensation preparation process for high-strength bio-based polyamide denim yarn fibers, including raw material coordination, a pre-polymerization stage, a deep polymerization stage, and an end-capping stage. This process achieves the construction of a uniformly distributed topologically branched network in a high-viscosity melt system by controlling the physicochemical environment during melt polycondensation. In the raw material coordination stage, the raw material system is fed into the polycondensation reactor. The raw material system includes a bio-based diacid monomer, a bio-based diamine monomer, and a branching modification component, wherein the bio-based diacid monomer is bio-based sebacic acid with an acid value of [value missing]. to Range, ash content not greater than The bio-based diamine monomer is bio-based pentanediamine, and its purity is not less than [missing information]. Moisture content not greater than The branched modification component was selected as a lignin-derived triamine with a three-symmetric structure. Before formal feeding, the physicochemical properties of the branched modification component were verified. The primary amine content of the lignin-derived triamine was determined by potentiometric titration, and its molecular weight distribution index was determined by gel permeation chromatography. To ensure that its primary amine content is within the range of to and Not greater than Within this range, thus providing a material basis for constructing branched nodes with symmetrical topological structures, the lignin-derived triamine undergoes potentiometric titration for incoming inspection, at a volume ratio of isopropanol to ethylene glycol. In the mixed medium, at concentration The sample was titrated with a perchloric acid standard solution. The equivalence point was determined by identifying the extreme point of the first derivative of the potential jump curve. The mass fraction of primary amine was calculated. The measured content of primary amine was lower than [a certain value]. At that time, a distillation column equipped with molecular sieve packing was used in to and Extracting the target fraction under vacuum to improve the molecular weight distribution index Not greater than , Weight-average molecular weight Number-average molecular weight ratio To address the issue of functional group density pretreatment locking the stoichiometric ratio for subsequent star-shaped topological structure formation, and to suppress local uncontrolled gelation or three-dimensional network defects caused by functional heterogeneity, the mass percentage of the branched modification component in the raw material system is [missing information]. to The molar ratio of bio-based sebacic acid to bio-based pentanediamine is controlled at... Compare to between.

[0028] In the steps During the pre-condensation stage, the environment of the condensation reactor is maintained at to Under normal pressure conditions, bio-based diacid monomers and bio-based diamine monomers undergo an amidation reaction to generate oligomers. During this process, the water produced in the reaction is continuously removed by a condenser until the number average molecular weight of the oligomers reaches a certain level. to Scope; in steps In the deep polycondensation stage, the process temperature is increased to to To overcome the mass transfer resistance caused by the increase in melt molecular weight, the polycondensation reactor employs a pulsed vacuum regulation method; when the vacuum level is... Under the following conditions, open the vacuum compensation valve. to The vacuum level will be reduced from [previous value] over a certain period of time. The following callback to Range; the pressure difference generated by this operation. This causes self-flash disturbance within the melt, leading to the migration of branched modified components into polyamide molecular chain segments, and increasing the pressure difference. The following relationship must be satisfied: ,in, This represents the pressure difference generated during the vacuum recovery process, in units of... ; ,in The vacuum level value after the callback, in units of ; The vacuum level value before the callback, in units of The pulsed vacuum regulation during the deep polycondensation stage is based on a pressure step response. Under no-load conditions, the pressure inside the polycondensation reactor is reduced to [a certain level]. The following quasi-steady state, according to Step gradient increases vacuum compensation valve opening percentage Record the pressure from the value before the callback. Rise to the value after pullback Required response time , This represents the valve opening percentage. and Units are , Units are Based on the measured data, a function relating valve opening degree to pressure rise rate was fitted to determine the relationship. to Preset valve opening amount The self-flash disturbance torque is locked by the physical stroke of the compensation valve, driving the branched modified components to uniformly penetrate and covalently bond into the molecular chain segments in the extremely high viscosity melt. This avoids melt hammering due to excessively fast vacuum recovery rate or insufficient mass transfer force due to excessively slow recovery rate. After completing the vacuum recovery, the system... The vacuum level will be restored to its original state. The following steps involve covalently bonding the branched modified component with the polyamide segments, with the above adjustment cycle occurring at intervals of [missing information]. Repeat the process once; during this stage, the fluctuation deviation of the agitator speed is maintained within ±2% of the preset reference speed.

[0029] When the stirring torque of the polycondensation reactor reaches the preset maximum process torque value At that time, execute the steps The end-capping operation is shown; bio-based vanillic acid monoester is added to the polycondensation reactor, and the reaction continues until the stirring torque is constant; the amount of bio-based vanillic acid monoester added is such that the ratio of terminal amino group content to terminal carboxyl group content of the obtained bio-based polyamide is [value missing]. to The bio-based polyamide produced by this process exhibits shear thinning properties in the molten state, and its shear rate decreases as the shear rate decreases. Increase to Within a certain range, its apparent viscosity decreases by no less than 50%. In the fibrous state, the uniformly distributed branched nodes constitute a three-dimensional stress diffusion system. When bio-based polyamide denim fibers are subjected to mechanical friction or acid and alkali erosion, the stress diffuses to adjacent molecular chains through the branched nodes, thereby reducing the risk of fibrillation.

[0030] In the polycondensation process, pulsed vacuum regulation is not only the driving force of reaction kinetics but also the core mechanism for controlling the uniformity of the spatial distribution of the topological structure. This invention introduces periodic vacuum level adjustments (from below 50 Pa to 500 Pa to 800 Pa) during the deep polycondensation stage. Utilizing the self-flash evaporation effect generated by the trace amounts of residual moisture in the melt during pressure jumps, a transient micro-turbulent flow field and isotropic shear force are created in the extremely viscous melt system. This micro-dynamic effectively overcomes the mass transfer resistance of the lignin-derived triamine component in the viscous fluid, forcibly driving it to cross the diffusion barrier and... The process achieves uniform penetration throughout the entire polyamide macromolecular chain, thereby eliminating the risk of uncontrolled crosslinking and microgel points caused by local enrichment of branching agents at the molecular scale. Compared with the constant high vacuum process commonly used in existing technologies, this pulsed dynamic control ensures that the branching nodes form a uniformly distributed star-shaped topological anchoring network in the polyamide matrix. This results in the product having excellent three-dimensional stress load transfer capability in the fibrous state, fundamentally inhibiting the single-chain force slippage of bio-based polyamide fibers under heavy washing and mechanical friction environments, significantly improving the anti-fiberization level and ensuring the color and strength stability of the fabric.

[0031] Example 1: In the continuous industrial production of high-strength bio-based polyamide denim yarn, when the system enters the deep polycondensation stage and the number-average molecular weight of the oligomers is close to the target value, the apparent viscosity of the melt increases exponentially with the degree of polycondensation. At this time, the lignin-derived triamine component in the raw material system generates a local enrichment gradient and diffusion inhibition phenomenon inside the reactor due to the decrease in diffusion coefficient. This non-uniform distribution leads to uncontrolled cross-linking of the melt in local areas, triggering microgel points that are sufficient to destroy fiber-forming properties. The traditional constant high vacuum method cannot break this high-viscosity mass transfer barrier, causing the fibers obtained from the polycondensation product to easily undergo fibrillation when subjected to the combined chemical and mechanical fields of subsequent indigo dyeing and stone washing processes, due to the lack of uniform physical anchoring points between molecular chains, exhibiting a trend of fiber surface peeling and strength attenuation. The polycondensation reactor implements a pulsed vacuum breathing control procedure in the deep polycondensation stage; with an acid value of to And the ash content is not greater than Bio-based sebacic acid with a purity of not less than And the moisture content is no greater than Bio-based pentanediamine is the main monomer, according to Compare The molar ratio of is added to the polycondensation reactor, and the mass percentage of is added. The lignin-derived triamine has a trisymmetrical structure; the primary amine content of the lignin-derived triamine is... to Its molecular weight distribution index Not greater than .

[0032] When the reactor temperature rises to And the vacuum level dropped to [a certain value] for the first time. The vacuum compensation valve at the top of the polycondensation reactor is in the following condition. The internal vacuum level will be actively adjusted back to At this point, the trace amounts of small-molecule byproducts remaining inside the melt undergo a self-flash evaporation effect due to the shift in pressure equilibrium. The resulting microscopic disturbance overcomes the mass transfer resistance of the high-molecular-weight polyamide melt. The microscopic shear force generated by this flash evaporation disturbance provides kinetic energy, driving the branched modified components to overcome mass transfer barriers and achieve their migration and distribution into the middle segment of the polyamide macromolecular chain. The vacuum level will be reset to [normal value]. The following steps involve covalently bonding the branched modified component, which is in a transiently activated state, with the polyamide segments; the pressure difference generated during this process... for ,satisfy The preset range This represents the pressure difference generated during the vacuum recovery process, in units of... ; ,in The vacuum level value after the callback, in units of ; The vacuum level value before the callback, in units of The above cycle is repeated every interval Repeat the process once until the stirring torque reaches the preset maximum process torque value. Adding 0.35% (w / w) of bio-based vanillic acid monoester to adjust the end-group properties stabilizes the ratio of terminal amino groups to terminal carboxyl groups in the resulting bio-based polyamide. The bio-based polyamide prepared by this method possesses a spatially uniform star-shaped topology; in the subsequent spinning process, the polyamide melt exhibits a shear rate that varies from... Increase to At that time, its apparent viscosity decreases nonlinearly with increasing shear rate, and the decrease is not less than 50%, reducing the melt conveying pressure in continuous production processes; uniformly distributed anchoring nodes construct a three-dimensional stress diffusion network in the fiber state. When denim fibers are subjected to the erosion of the high acid and alkali environment of indigo dyeing or the strong friction of stone washing, the stress is transferred globally through the topological nodes, inhibiting the force slippage and breakage of single linear chains; this fiber undergoes After simulating heavy washing of denim, the fiber surface remained smooth and the strength did not decrease, avoiding the risk of fibrillation of bio-based polyamide under heavy washing.

[0033] Example 2: In the experiment verifying the distribution of branched components in high-strength bio-based polyamide denim yarn fibers under high viscosity conditions, the experimental platform was selected with a volume of [missing information]. The polycondensation reactor, equipped with a pressure sensor and torque monitoring unit, receives data from an integrated vacuum gauge and a torque transmitter for the stirring motor. The vacuum gauge has a measurement range of [missing information]. to Pressure resolution is The torque transmitter has a range of [range missing]. to The sampling frequency is set to To simulate electromagnetic noise interference in a real industrial production line environment, a signal-to-noise ratio of [value missing] was superimposed in the sensor signal link during the experiment. Gaussian white noise.

[0034] Setting the pressure difference during the deep polycondensation stage At that time, the purpose is to balance the intensity of the disturbance caused by the self-flash evaporation of small molecules inside the melt with the stability of the reactor's water removal rate; when the pressure difference is... Setting tends to the lower limit At this time, the microscopic shear force generated inside the melt weakens, resulting in limited diffusion displacement of lignin-derived triamines in high-viscosity systems; when the pressure difference... Setting tends towards the upper limit At the same time, drastic fluctuations in system pressure can lead to frequent interruptions of the water removal kinetic equilibrium, prolonging the reaction cycle and inducing the risk of polyamide thermal degradation; this experiment will use pressure difference... Set as The vacuum level value after the callback for Vacuum level value before pullback for Material input parameters: acid value. The bio-based sebacic acid and water content are Bio-based pentanediamine; during the experiment, the system every Initiating a vacuum conditioning cycle, via the vacuum compensation valve... The internal vacuum level will be changed from Adjust as follows ,exist Internal reset; during this process, the transient fluctuation amplitude output by the torque monitoring unit is used as an indicator to characterize the intensity of self-flash evaporation interference inside the melt; the experimental group is set up with gradient sample groups within the range defined by this invention, and a control group with missing pulse vacuum control or branching group distribution ratio exceeding the tolerance is set up simultaneously.

[0035]

[0036] According to the data in Table 1, the content of branched modified components in samples 1 to 3 of this invention is at a certain level. to Within the range, combined with pulsed vacuum control, it generates a value greater than The decrease in apparent viscosity indicates that the system constructs a uniform quasar topological network; control group 1 has a lower branching node density than control group 1. The inability to form an effective stress diffusion network resulted in a viscosity reduction of only [percentage missing]. Control group 2 had a branched component content that reached [a certain level]. Excessive cross-linking induced by pulse perturbation caused the torque fluctuation amplitude to rise abnormally. This leads to a decrease in fiber-forming performance and an increase in fibrillation level; control group 3, although maintaining the recommended ratio, used a traditional constant vacuum method, and the torque fluctuation amplitude was only [missing value]. This indicates that in the absence of microscopic self-flash evaporation disturbance, branched components become locally enriched and cannot achieve nonlinear transformation of rheological properties.

[0037] Example 3: This example combines Figures 1 to 3 The polycondensation preparation process of a high-strength bio-based polyamide denim yarn fiber is described, as follows: Figure 1As shown, step 101, the raw material coordination stage, includes a bio-based dicarboxylic acid (sebacic acid) with an acid value of 548 mg KOH / g to 552 mg KOH / g, a bio-based diamine (pentanediamine) with a purity ≥99.5%, and a branched modified component, lignin-derived triamine, with a content of 0.15% to 0.45% and a trisymmetrical structure. The primary amine content of this branched modified component is 12.5 wt% to 13.8 wt%, and the molecular weight distribution index (PDI) is ≤1.2. Step 102, the pre-condensation stage, is at 210... Up to 230 Under normal pressure, a condenser continuously removes the reaction water, allowing sebacic acid at a molar ratio of 1.0:1.01 to 1.03 to react with pentanediamine to produce oligomers with a number-average molecular weight (Mn) of 2000 to 5000. The core reaction region is a polycondensation reactor equipped with real-time torque monitoring, connected to a temperature of 265°C. Up to 280 Step 103 is the deep polycondensation stage, which includes a pulsed vacuum conditioning cycle, by adjusting the vacuum level from below 50 Pa to 500 Pa to 800 Pa within 15 to 20 seconds. The component migration is driven by a self-flash perturbation of 450 Pa to 750 Pa, and the vacuum is restored to below 50 Pa within 10 seconds to promote covalent bonding until the torque reaches 92% of the preset maximum value. Finally, bio-based vanillic acid monoester is added in the end-capping stage of step 104 and reacted until the torque is constant, outputting an antigen fibrillation final product with an end amino to end carboxyl ratio of 0.95 to 1.05, a viscosity reduction of ≥50%, and a star-shaped topology.

[0038] like Figure 2 As shown in the figure, the left vertical axis represents the torque fluctuation amplitude in N·m and the apparent viscosity decrease in % (%), respectively. The right vertical axis represents the fibrillation level, and the horizontal axis lists five sample groups with branched modified component mass percentages of 0.15%, 0.30%, 0.45%, 0.10%, and 0.55%. The legend shows that horizontal bars represent torque fluctuation amplitude, vertical bars represent apparent viscosity decrease, and diagonal bars represent fibrillation level. The data shows that in the range of 0.15% to 0.45%, as the torque fluctuation amplitude remains at a low level, the apparent viscosity decreases and the fibrillation level remains low. In the 0.10% low content group, the apparent viscosity decrease is extremely low and the fibrillation level is relatively high. In the 0.55% high content group, the torque fluctuation amplitude increases sharply and the fibrillation level reaches the highest value.

[0039] like Figure 3 As shown, in step 101, a raw material system comprising a bio-based dicarboxylic acid, a diamine, and 0.15% to 0.45% lignin-derived triamine is incorporated. The process proceeds to step 102, at 210... Up to 230 Under normal pressure and dehydration conditions, pre-condensation produces oligomers with a number-average molecular weight of 2000 to 5000, which then proceed to step 103, the deep condensation stage, at 265°C. Up to 280 The process involves periodic vacuum adjustment. The block diagram of the pulsed pressure disturbance mechanism associated with this step shows that the self-flash disturbance is induced by adjusting the vacuum level from 500Pa to 800Pa to drive the uniform migration and bonding of the branched modified components. The process then enters the torque monitoring and judgment box to determine whether 92% of the preset maximum process torque value has been reached. If not, step 103 and pulse adjustment are repeated every 15 minutes. If so, the process proceeds to step 104, the end-capping modification reaction is carried out, bio-based vanillic acid monoester is added and reacted until the torque is constant. Finally, high-strength bio-based polyamide denim yarn fiber with an isotropic topology is output.

[0040] Example 4: In the system calibration procedure for a high-strength bio-based polyamide denim yarn fiber production line, the system determines a preset maximum process torque value; the calibration procedure applies to the raw material system, which includes an acid value... Bio-based sebacic acid with a purity of Bio-based pentanediamine; implementation environment: equipped with a torque sensor. Polycondensation reactor; first, a baseline viscosity rise test was conducted, and the temperature was raised to [temperature value missing] without the addition of branched modified components. And maintain Vacuum is used to record the change in the output torque of the stirring motor caused by the increase in the molecular weight of polyamide; when the real-time data from the torque sensor shows a non-linear step and the slope increases, it is determined that the melt has reached the critical processing viscosity, and this value is recorded as the reference torque value. The second phase introduces a quality percentage of... For lignin-derived triamines, a decrease in melt torque compared to linear systems was observed at the same number-average molecular weight. Based on this, the maximum process torque value will be preset. The product number average molecular weight was defined as reaching The torque measurement value at that time; as specified above. The threshold is a safe operating point to ensure that the melt is capped before uncontrolled gelation occurs.

[0041] To verify the driving mechanism of pulsed vacuum control on the branching node distribution, pressure differential was applied during the deep polycondensation stage. Dynamic response test; initial state is set as vacuum degree. The quasi-steady melt, at which point the lignin-derived triamine component has a diffusion coefficient that decreases to... Localized stagnation occurs due to the magnitude of the problem; opening the vacuum compensation valve and adjusting the valve step size maintains the vacuum level inside the vessel within a certain range. Internally The following callback This operation utilizes the pressure increase to induce a momentary flash evaporation of trace amounts of water dissolved in the melt. This time window covers the kinetic cycle of microbubbles from nucleation to bursting. The localized microturbulence generated by the flash evaporation produces a transient shear field in the extremely viscous melt, driving the branched modified components to cross the diffusion barrier and migrate towards the middle segment of the polyamide molecular chain. The rapid extraction operation restores the vacuum level to Below, a spatially isotropic quasar topology network is constructed. Table 2 shows the test records of the effect of different calibrated torque percentages on the product strength and fibrillation properties.

[0042] Table 2: Test Records of Product Strength and Fibrillation Properties under Different Calibrated Torque Percentages

[0043]

[0044] Based on the data analysis in Table 2, when the end-capping trigger threshold is set to... At that time, the tensile strength of the fiber is And the fibrillation level is This indicates that the branched nodes achieve uniform anchoring at the molecular level; if the threshold is increased to Because the branching point density becomes locally supersaturated in the later stages of the reaction, the fibrillation order rises to [a certain value]. Level, Judgment The preset maximum process torque value is the control criterion for balancing fiber strength and topological regularity; the product under this state exhibits nonlinear rheological properties, and its shear thinning behavior conforms to the following power-law equation: ,in, Apparent viscosity, in units of ; Shear rate, in units of ; This is the consistency coefficient; In this embodiment, the shear-thinning index is used. Under the end-cap node, The value stabilizes at The apparent viscosity reduction under the high shear field at the discharge port reached [value missing]. .

[0045] Example 5: In an application scenario involving the switching production of different batches of bio-based pentanediamine and bio-based sebacic acid monomers, fluctuations in the residual moisture content of the material cause interference with the initial melt viscosity. The polycondensation system executes a standardized torque benchmark normalization method; the normalization method is applied when the number average molecular weight of the oligomer reaches a certain level. Start at the specified time, through Maintaining a constant speed for the agitator at the specified temperature, the steady-state output signal of the torque transmitter is acquired and recorded, and this signal is defined as the zero-point reference value. Real-time measurement of stirring torque during the deep polycondensation process. With zero reference value The difference is used to calculate the effective torque component. The system calculates the effective torque component based on the preset maximum process torque value. The proportion of the end cap node is used to determine the torque determination error caused by batch differences in materials.

[0046] When the size of the polycondensation reactor is increased or the configuration of the stirring device is adjusted, the preset reference rotation speed is required. The rheological calibration procedure is determined by performing the calibration; the calibration procedure measures the apparent viscosity of the melt at the deep polycondensation initiation point. By executing a step-scan program at different rotational speeds, torque response data under different speed gradients are obtained, and a correlation between stirring torque and shear rate is established. Based on this correlation data, the system determines the rotational speed setpoint that meets the constant shear field requirement and calibrates this setpoint as the preset reference rotational speed. During the subsequent deep polycondensation stage, the fluctuation deviation of the agitator speed was maintained within the preset reference speed. of Within a certain range, ensure that the branched modified components and polyamide segments bind at a constant shear rate, and suppress the localized uncontrolled gelation of the melt.

[0047] Example 6: In the process of calibrating the dynamic response characteristics of the vacuum regulation system, the control system adjusts the opening degree of the vacuum compensation valve. A mapping model between the valve opening degree and the rate of pressure rise inside the reactor is established by performing multiple pressure step tests under no-load conditions in the polycondensation reactor. This calibration procedure evacuates the vacuum level inside the reactor to... The following steps maintain a constant value, sequentially setting the valve opening to a percentage of the total opening. arrive And the step gradient is Record the pressure inside the vessel from Revert to vacuum level after the callback The actual response time required, of which The vacuum level value after the callback, in units of The system determines whether the conditions are met based on the measured time data. to The control parameters required by the callback timing are fixed to the controller. During the deep polycondensation process, the calibrated valve opening is used as the only input value to ensure that the micro-shear force generated by the self-flash disturbance reaches the physical strength to overcome the mass transfer resistance.

[0048] When the production line faces fluctuations in melt thermal stability during continuous operation, the monitoring system executes standardized online stability monitoring procedures; it collects real-time measurements of the stirring torque. The rate of change of torque over time was calculated during the pressure holding phase of each pulse vacuum regulation cycle. This is a real-time measurement of torque, in units of... The system quantifies and compares the measured rate of change with the baseline slope. If the observed torque growth slope is below the set threshold for two consecutive cycles and the measured value... Failed to reach the preset maximum process torque value of Nodes converge, among which This is the preset maximum process torque value, in units of... If the material is found to be at risk of local thermal degradation, the controller will trigger the abnormal handling logic and automatically increase the pumping rate of the vacuum compensation valve to accelerate the material discharge process.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber, characterized in that, Includes the following steps: Step 101: The raw material system is fed into the polycondensation reactor. The raw material system includes bio-based dicarboxylic acid monomer, bio-based diamine monomer, and branched modification component. The branched modification component is a lignin-derived triamine with a three-symmetric structure, and the mass percentage of the branched modification component in the raw material system is 0.15% to 0.45%. Among them, the bio-based dicarboxylic acid monomer is bio-based sebacic acid with an acid value of 548 mg / g to 552 mg / g and an ash content of no more than 0.01 wt%, and the bio-based diamine monomer is bio-based pentanediamine with a purity of no less than 99.5% and a moisture content of no more than 500 ppm. Step 102: Under normal temperature and pressure conditions of 210°C to 230°C, the bio-based dicarboxylic acid monomer and the bio-based diamine monomer are reacted to generate oligomers. Step 103: Under conditions of 265℃ to 280℃, periodically adjust the vacuum level in the polycondensation reactor to induce deep polycondensation of the oligomers. A single adjustment cycle includes: opening the vacuum compensation valve, adjusting the vacuum level from below 50 Pa to 500 Pa to 800 Pa within 15 to 20 seconds to induce self-flash turbulence inside the melt, and restoring the vacuum level to below 50 Pa within 10 seconds; repeating the adjustment cycle every 15 minutes until the stirring torque of the polycondensation reactor reaches 92% of the preset maximum process torque value. Step 104: Add 0.15% to 0.55% by mass of bio-based vanillic acid monoester into the polycondensation reactor and continue the reaction until the stirring torque is constant.

2. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, The primary amine content of the branched modified component is 12.5 wt% to 13.8 wt%, and its molecular weight distribution index is not greater than 1.

2. In step 103, the stirring speed of the polycondensation reactor is controlled so that the shear rate of the melt during the bonding stage between the branched modified component and the oligomer is kept constant. The fluctuation deviation of the stirring speed is controlled within ±2% of the preset reference speed to suppress uncontrolled gelation of the melt in a localized manner.

3. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 103, the self-flash evaporation disturbance generated by the vacuum degree correction process drives the branched modified component to migrate to the middle segment of the polyamide molecular chain, so as to form spatially uniformly distributed branched nodes.

4. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, The molar ratio of bio-based sebacic acid to bio-based pentanediamine is 1.0 to 1.01 to 1.

03.

5. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 103, during the pressure holding stage after the vacuum level is restored to below 50 Pa, the branched modified component and the polyamide segment are covalently bonded.

6. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 103, when the mass percentage of the branched modified component in the raw material system is 0.25% to 0.35%, a branched polyamide with a star-shaped topology is obtained.

7. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 104, the amount of bio-based vanillic acid monoester added is such that the ratio of the terminal amino group content to the terminal carboxyl group content of the resulting bio-based polyamide is 0.95 to 1.

05.

8. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 102, the water produced by the reaction is continuously removed by a condenser until the number average molecular weight of the oligomer reaches 2,000 to 5,000.

9. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, In step 103, the pressure difference generated during the vacuum degree recovery process The following relationship must be satisfied: ,in, , This is the vacuum level value after the callback. This represents the vacuum level value before the callback.

10. The polycondensation preparation process for high-strength bio-based polyamide denim yarn fiber according to claim 1, characterized in that, The prepared bio-based polyamide, in the molten state, exhibits a non-linear decrease in apparent viscosity with increasing shear rate, and the viscosity decreases further as the shear rate increases from... Increase to Within the specified range, the apparent viscosity decreases by no less than 50%.

Images